Intermittency during plastic flow is one example of avalanches in critically evolving systems. Such fluctuations are typically assessed statistically with scale-free distributions. Theory and simulations have studied this behavior in detail, generally arguing for two prominent models (mean-field approach or a jamming-unjamming picture) that are characterized via distinctly different avalanche scaling exponents. In this paper, the authors show experimentally how scaling exponents for the same single crystalline metal can admit a variety of scaling exponents that encompass both models. Depending on both intrinsic and extrinsic factors, their experiments reveal how the scaling exponents are nontrivial and therefore not universal.

In this paper, Brillouin light scattering (BLS) characterization revealed an unusual decrease in the speed of sound in an Ag-polystyrene nanohybrid material with increasing filler content. The hybrid material possesses an isotropic and well-defined nanoparticle distribution based on its particle-brush architecture. Temperature-dependent BLS measurements reveal the unique contribution of local thermoplasmonic heating caused by the Ag nanoparticles exposed to laser irradiation. This reversible thermoplasmonic effect implies a lower apparent glass transition temperature (Tg) measured by means of BLS. Furthermore, irreversible aggregation and redispersion of the Ag nanoparticles were observed at temperatures much higher than Tg. This aggregation-redispersion effect is also reflected in a change of the mechanical properties, demonstrating its intimate interplay with the hybrid composite structure.

Kikuchi diffraction patterns are formed by backscattered electrons in the scanning electron microscope and can provide local crystallographic information with submicrometer spatial resolution. The authors present a new method to estimate local lattice parameter variations in materials by comparison of experimental Kikuchi patterns with projectively transformed simulations. As an application example, they analyze the local tetragonality in a steel sample containing martensite grains with a body-centered tetragonal (bct) structure and austenite regions with a face-centered cubic (fcc) structure. The image shows the best fit of a projectively transformed bct reference simulation to an experimental fcc Kikuchi pattern.

Epitaxial growth of single-layer transition metal dichalcogenides can give rise to high-quality, large area materials, and it is even possible to grow them in just a single orientation—the key to exploit properties such as the valley degree of freedom. However, the strong interaction with the substrate that favors a single orientation can also destroy the interesting properties of the material due to hybridization effects. Here this issue is resolved by first growing a single layer of WS${}_2$ on Ag(111) and then decoupling it from the surface via the intercalation of Bi atoms.

Topological Dirac semimetals, such as Cd${}_3$As${}_2$, possess gapless Dirac nodes in the bulk and topologically protected surface states. In this study, the authors show that the magnetotransport properties of epitaxial thin films of Cd${}_3$As${}_2$ depend sensitively on the nature of the exposed film surface. For example, it is shown that nitrogen plasma passivation allows for observation of the quantum Hall effect from the surface states. The results highlight the importance of band bending and surface chemistry in the relative contributions from surface and bulk states to the measured transport properties.

The emergent ferroelectricity in HfO${}_2$-based systems now offers new possibilities beyond high-k dielectricity. In this study, the authors use field-dependent pyroelectric measurements to first prove the polar and ferroelectric nature of the material and then elucidate the role of defect dipoles on the wakeup phenomenon in Si-doped HfO${}_2$ thin films. This study further reports the first-ever direct measurements of the electrocaloric effect in HfO${}_2$-based systems. A four-fold larger electrocaloric response, in comparison to its thermodynamic converse, pyroelectricity, suggests that the defect dipoles can contribute an additional configurational or dipolar entropy potentially useful for solid-state cooling technologies.

Based on density functional theory calculations, the authors develop a general model for nucleation of III-V semiconductors on vicinal nonpolar (111)-oriented substrates. This model predicts, in particular, that the atomic structure of the step edges at the substrate surface is decisive for the formation and suppression of detrimental rotational twin defects. These predictions are in full agreement with the experimental analysis done on a series of samples with the technologically important material combination of GaP grown on As-modified Si(111). The authors thus derive a complete picture of the formation and suppression of rotational twins relevant for low-defect III-V-on-Si integration.

Dopants in metal oxide materials can dramatically modify material properties in many important applications. Yet determination of dopant sites at the atomic scale, especially at the dilute regime, remains challenging. The authors combine x-ray absorption near-edge structure spectroscopy experiment and theoretical modeling to demonstrate that in the dilute Mn-doped lithium titanate, a promising lithium-ion battery material, the dopant Mn${}^{2+}$ ions reside on tetrahedral sites. A substantial 20% decrease in electrochemical capacity was observed as compared to the pristine sample

Much is being currently written about machine learning applied to materials science, but, what is machine learning? It is certainly not physics, chemistry, or materials science, in which case how do these sciences enter? In this Research Update the authors examine what machine learning is and is not, review several applications of machine learning methods for predicting new materials, noting some of the cases where the predictions have been experimentally validated, and illustrate the spectrum of applications possible. The emphasis is on the broader picture where they discuss some newer methods and more importantly reference their successes. Thus, the paper looks more towards the future than to the past, sharing some of the lessons the authors have learned from their own experience in the field.

Cadmium arsenide is a time-honored material within condensed matter physics, with the first investigations dating back to the thirties. Nowadays, after theorists predicted a pair of symmetry-protected three-dimensional Dirac cones in its band structure, cadmium arsenide is going through an intense revival. Cadmium arsenide is now thought of as a three-dimensional analogue of graphene. Several experimental studies showed compelling evidence of conical bands in this material, revealing a number of interesting properties and phenomena. To interpret them correctly, a detailed understanding of the basic material parameters has become even more important than before. To this end, the authors extensively review the past and current knowledge of cadmium arsenide. They start with the crystal lattice properties, and continue with the technological aspects of its crystal growth. This is followed by a discussion of the theoretical and experimental results, leading to different possible views of this material’s electronic bands.